Process for the granulation of an animal feedstuff additive

ABSTRACT

The invention relates to a process for the granulation of an animal feedstuffs additive comprising amino acids or vitamins in a circulating fluidized bed, wherein the additive is preferably a fermentation product and optionally comprises further constituents from the fermentation broth.

FIELD OF THE INVENTION

The invention relates to a process for the granulation of an animalfeedstuff additive comprising amino acids or vitamins in a circulatingfluidized bed, wherein the additive is preferably a fermentation productand optionally comprises further constituents from the fermentationbroth.

BACKGROUND OF THE INVENTION

Animal feedstuffs are supplemented with individual amino acids accordingto the requirement of the animals. For supplementing animal feedstuffs,e.g. with L-lysine, L-lysine monohydrochloride having an L-lysinecontent of 78% is predominantly employed to date. Since L-lysine isprepared by fermentation, for the preparation of the monohydrochlorideit must once initially be separated off from all the other constituentsof the crude fermentation broth in expensive process steps and thenconverted into the monohydrochloride, and the latter must becrystallized. A large number of by-products and the reagents needed forthe working up are produced as waste by this procedure. Since a highpurity of the animal feedstuff supplement is not always necessary andfurthermore the by-products of the fermentation often still comprisenutritionally active valuable substances, there has therefore been nolack of attempts in the past to convert L-lysine together withconstituents of the fermentation broth into a solid animal feedstuffless expensively.

The complex composition of such media has proved to be a seriousdisadvantage in the processing. These generally can be dried only withdifficulty, and the dried products are often hygroscopic, practicallynot free-flowing, at risk from the formation of lumps and unsuitable forthe industrially demanding processing in mixed feedstuff plants. Theproducts from the fermentation for the preparation of lysine are to bementioned above all here. Simple dewatering of the crude fermentationbroth by spray drying leads to a dusty, highly hygroscopic concentratewhich is lumpy after a short storage time and cannot be employed as ananimal feedstuff in this form.

The use of a spray dryer with an integrated fluidized bed gives finelydivided and porous but free-flowing spray particles with a very low bulkdensity and a still high hygroscopic nature. A considerable dustnuisance arises in the handling of this product.

Build-up granulation in a fluidized bed has also proved to be not verysuitable, since here also large amounts of additional substances (as arule more than 10 wt. %) are necessary, these being added continuouslyaccording to DD 268 856. The use thereof in this context is essential inparticular in order to bind the water from the fermentation broth and inthis way to prevent the granules from forming lumps, which would have anadverse effect in the case of build-up granulation in particular.

Further processes for the granulation of animal feedstuff additivescomprising amino acids and based on fermentation broth are known fromU.S. Pat. No. 4,777,051, EP 0 615 693 B and EP 0 533 039 B.

U.S. Pat. No. 4,777,051 discloses a spray drying process with asubsequent additional drying step. Solutions of tryptophan or threonineof varying origin having a content of 20-60 wt. %, based on the totalsolids content, are sprayed in a first step to give semi-dry granuleshaving a residual moisture content of 5-15%. The moist granules are thenspread out on a conveyor belt dryer with a perforated base and finallydried with hot air, a product having a residual moisture content ofabout 4 wt. % being obtained.

Drying is accordingly carried out in an expensive manner in two stagesin two different apparatuses.

According to EP 0 615 693, the granulation is also carried out in atwo-stage drying process.

The fermentation broth is spray dried, optionally after removal of someof the constituents, to give fine particles which have a maximumparticle size of 100 μm to the extent of min. 70 wt. %, and the fineparticles obtained in this way are built up in a second stage to givegranules which comprises fine particles to the extent of min. 30 wt. %.

In addition to the two-stage nature of the drying granulation process,the disadvantage of this process is that the granulation can be carriedout only batchwise and not continuously.

EP 0 809 940 B1 also discloses a process for the granulation of ananimal feedstuff additive based on fermentation broth. The process ischaracterized in that the fermentation broth is granulated, compactedand dried in a fluidized bed in one step, while an amount of energysufficient to establish a desired particle diameter and a desired bulkdensity is introduced into the fluidized bed by a mechanical route, inaddition to the energy required for generation of the stationaryfluidized bed.

An essential feature of fluidized bed spray granulation is the formationof a stable fluidized bed within the granulator. This means that thespeed of the inflow medium must be chosen such that fluidization of theparticles to be dried occurs, but pneumatic conveying is avoided. It isthus ensured that the particles formed indeed are not discharged, but aconstant change in place of the particles takes place, so that there isa uniform probability of impingement for the drops sprayed in.

This process has the known disadvantages of fluidized bed spraygranulation. These are chiefly:

As the particle size decreases, the speed of the inflow medium must begreatly reduced, so that a stable stationary fluidized bed is maintainedand discharge of the particles from the granulator is avoided. Since inthis process the inflow medium is the energy carrier, the efficiencydecreases to an extreme degree. The build-up rates which can be achievedare too low for the granulation process still to be able to be operatedeconomically.

A process of this type is described in U.S. Pat. No. 4,946,654. A lossof material due to the discharge of dust is avoided by separating thisoff from the gas flowing out of the granulator and recycling it into thefluidized bed.

The lines have dimensions such that only small amounts of solid can befed back.

SUMMARY OF THE INVENTION

The object of the invention is to provide an efficient process for thegranulation of an animal feedstuffs additive comprising amino acids andvitamins which can be carried out continuously, the additive preferablybeing a fermentation product and optionally comprising furtherconstituents incl. the biomass from the fermentation broth.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a process for the granulation of L-amino acidsand vitamins, in particular chosen from the group consisting ofmethionine, L-lysine, L-threonine, L-arginine, L-tryptophan or calciumpantothenate or pantothenic acid (vitamin B5), which is characterized inthat the granulation is carried out in a circulating fluidized bed, by aprocedure in which

-   a) an aqueous suspension or an aqueous solution of an amino acid or    a vitamin is sprayed in a granulator chamber containing the    fluidized bed,-   b) at least 10 wt. % of the particles in the granulator chamber are    discharged with the drying gas,-   c) the particles discharged are then separated off from the gas    stream,-   d) the particles separated off from the waste gas stream are fed    back to the chamber and-   e) granulated particles having a size within the desired particle    size range are taken off continuously from the chamber, preferably    downwards, so that the amount of solid in the chamber remains    constant.

Advantageously, the drying gas flows through the chamber against theforce of gravity and is passed into the chamber via an inflow base witha temperature in the range from 100 to 450° C., preferably 150 to 350°C.

In contrast to the prior art, according to the invention granulation iscarried out in this manner not in a stationary fluidized bed but in acirculating fluidized bed (CFB). This means that the inflow speed of thedrying gas stream is adjusted such that 10 to 100 wt. %, preferably 30to 100 wt. %, in particular 50 to 100 wt. % of the solid particles,based on the fluidized bed in the granulator chamber, leave this chamberupwards continuously and are then separated off from the gas stream andrecycled into the granulator chamber.

The inflow speed necessary for the discharge depends on the particlesize and the density of the particles and is in general 1 to 10 times,preferably 1 to 4 times the speed necessary also to allow particleswhich do not belong to fine dust (<100 μm) to circulate with the dryinggas stream in the desired amount. These are in particular particleswhich have not yet reached the desired final size.

In the conventional fluidized bed processes (e.g. U.S. Pat. No.4,946,654) only very small amounts of fine dust are blown out and theparticles having a particle size distribution in the region of >100 μmremain in the fluidized bed and are taken off from this, but notcirculated.

According to the invention, particles having particle sizes of <and >100 μm, if desired also in the range from 250 μm to 600 μm, areconveyed upwards in the desired amount and circulated.

According to the invention, the circulation rate per hour in generalcorresponds to 2 to 100 times, in particular 5 to 50 times the masshold-up in the granulator chamber. According to the prior art, incontrast the value for this parameter in the fluidized bed is <2. Theupper limit of the inflow speed is determined by the given parameters ofease of operation of the apparatus.

It has also been found that by the additional introduction of mechanicalenergy into the fluidized bed, a less intensive granule growth or anevening out of the particle diameters and an increase in the bulkdensity are achieved.

The granulation process is particularly advantageously carried out suchthat the additional energy is introduced into the fluidized bed in thegranulation chamber by movable flat structures. These can be rotatingknives, vanes, blade surfaces, flat iron bars or compacters installed inthe chamber of the fluidized bed. It is possible here for the knives,blades, flat iron bars, compacters or the like to be driven mechanicallyand in this way to achieve a constant comminution of the granulationparticles, so that the particles of the fluidized bed remain below acertain particle size. However, all other tools familiar to the expertwhich, for example, can be immersed directly in the fluidized bed arealso possible. The use of rotating screws or mixing tools with highshearing forces is thus conceivable, these tools also acting on theparticles or granules in the fluidized bed and interacting with theparticles.

The CFB process is known above all from heterogeneous catalysis usingfinely divided catalysts or combustion technology, but not for theformation of granules of organic compounds.

The solids to be granulated are animal feedstuffs additives, preferablyamino acids and vitamins. In the case of amino acids, preferablyL-arginine, methionine, L-lysine, L-threonine and L-tryptophan, and inthe case of vitamins, preferably calcium pantothenate (vitamin B5) orpantothenic acid.

Concentrated aqueous solutions or suspensions of the purified compoundsfrom chemical and fermentative production having a purity of the solidof 80 to approx. 99.5%, as well as concentrated fermentation broths areemployed here. As described in EP 0 809 940 B1 and EP 615 693 B1 inparticular for L-lysine, in addition to these compounds the fermentationbroths optionally also contain further constituents of the fermentationbroth, as well as the biomass. However, the biomass can also havealready been completely or partly separated off.

It has been found that in contrast to known processes of stationaryfluidized bed spray granulation, with the solids mentioned high build-uprates and therefore an efficient process can also be realized forparticles having a relatively low average diameter of e.g. 100 to 400 μmwith the process according to the invention. Even particles in the sizerange below 100 μm are accessible via a fluidized bed spray granulation.

The efficiency of the process also depends on the solids content in thesolution introduced. As the solids content increases, the amount ofwater to be evaporated drops. The energy requirement necessary for thegranulation is reduced and the apparatus can be smaller in construction.For relatively poorly soluble solids, such as e.g. L-threonine(solubility at 85° C. approx. 19%), the solubility and therefore theefficiency of the process has been found in superheating of the mediumintroduced. Using a special nozzle arrangement, a pre-pressure of 1 upto 5 bar is generated in the feed line to the nozzles, rendering heatingto above 100 to 160° C. possible. The special two-component pressurenozzle operated with compressed air has an extended liquid insert with atriple-groove whirling body. The whirling body has dimensions and isadjusted such that the free cross-section which the liquid must pass isas large as possible and nevertheless a high drop in pressure of up to 5bar is achieved in the liquid zone under operating conditions. At thesame time, in spite of this build-up, solid particles contained in thefluid having a particle size of up to 50 μm can pass through the nozzle.The atomization of the liquid passing through the whirling body takesplace pneumatically by expansion of compressed air in the annular gaparound the liquid insert.

The solubility of L-threonine increases to approx. 32% at 120° C.Surprisingly, even in the case of heat-sensitive amino acids andvitamins, decomposition reactions and therefore product losses have notbeen found at all here during the progress of the granulation.

The increase in the solids concentration can also take place by the useof suspensions of the corresponding solid in a saturated solution of thecorresponding solid. This can be produced by super-concentration of asolution containing the solid by evaporation etc.

addition of the solid to a saturated solution of the solid.

If suspensions are employed, a small particle size (in general 10-30 μm)of the undissolved solids content offers advantages in the production ofstable granules. If necessary, the particle size of the undissolvedcontent can be reduced accordingly by prior dry grinding of the solidscontent added

wet grinding in the suspension, preferably by only one pass through thegrinding organ in the feed line to the spray nozzle.

With the process described it is possible to process suspensions havingsolids concentrations of up to more than 70 wt. %.

Suspensions having a content of 25 to 60 wt. %, based on the totalamount of the suspension, are preferably employed.

Surprisingly, it has been possible also to produce granules with therequired properties from solutions or suspensions of very pure solids(up to 99.5%) without the addition of binders or other auxiliarysubstances using the process described.

The invention also provides a device for carrying out the processaccording to the invention, which has the following features:

-   a) a cylindrical or rectangular granulator chamber having a    diameter/height ratio of 1:1 to 1:5 (in the case of the rectangular    construction the dimensions are width:length:height of 1:1:1 to    1:8:5), which contains an inflow base,-   b) an atomizer organ for the suspension or solution arranged in this    chamber,-   c) feed organ for the fluidizing or drying medium-   d) a discharge opening for the product to be recycled arranged in    the upper part of the chamber,-   e) a solids separating system which is connected to the chamber via    this discharge opening, and which contains a waste air pipe,    optionally provided with a filter unit, for removal of the gas    stream,-   f) a return feed for the product to be recycled, which, starting    from the discharge opening, opens in the lower part of the chamber,-   g) optionally a sifter which is installed at the lower part of the    chamber.

The device comprises a preferably tall granulation chamber 1 having awidth to length to height ratio of 1:1:1 to 1:8:5, preferably 1:6:3. Itis provided with a suitable inflow base at the lower end. The pressureloss of the base must be such that the inflow medium is distributeduniformly over the complete apparatus cross-section and no dead zonesare present. After a further rectangular or cylindrical part, which canalso be of extended construction expanding to twice the width ordiameter, the waste gas feed of the granulator opens into the separatorsystem, for example via one or more separating cyclones connected inseries and a waste air filter into the circulating gas line or the wastegas chimney. The solids separators are provided with solids return linesinto the granulation chamber just above the inflow base. Suitableapparatuses, such as, for example, bucket wheel sluices, are employedfor pneumatic closure of the solids separators. The granulation chamberis supplied with hot drying gas (for example flue gas, air, nitrogen)via a fan and a suitable gas heater.

A sifting discharge pipe, which can have diverse shapes, is preferablyinstalled centrally at the lower end of the granulation chamber andopens in a recess of the inflow base. It can be provided with baffles tointensify the sifting performance, or connected to a sifting chamber. Adefined sifting upwards flow can be established in the sifter pipe via agas supply independent of the main stream. The solid can be dischargedagainst this flow via a further pneumatic closure.

In order to produce approximately spherical particles, it isadvantageous to divide the suspension or solution into very finedroplets. Pneumatic nozzles and pressure nozzles can be employed foratomization of the suspension or solution. A combined two-componentpressure nozzle is preferably employed, the suspension being conveyed tothe nozzle via a multi-stage low-pulsation high pressure pump. Athree-component nozzle or multi-component nozzle can also be employed.The pressure insert of this nozzle should be such that a high drop inpressure is achieved with the flow rates under operating conditions. Inorder to obtain a very fine spray, the pressure atomization is alsooverlapped here by an additional two-component atomization by means ofcompressed air.

The nozzle preferably sits at the bottom above the inflow base centrallyin the middle of the granulation chamber over the sifter opening withthe spray direction upwards. The nozzle stream and therefore the openingangle can be adjusted with an adjustable air cap.

The granulation of solids in the circulating fluidized bed (CFB) iscarried out in the manner described in the following. It is essentialthat the inflow speed of the hot drying gas in the granulation chamberis preferably significantly higher than the discharge speed ofgranulating particles.

A solids-containing suspension or solution is sprayed with the nozzleinto the granulation chamber, which is operated with hot drying gas andis either still free from solids or already provided with an initialfilling of fine particles. The liquid evaporates there and solidsremain. The particle stream forming in the granulation chamber isdischarged from this chamber in an amount of up to 100% and thenseparated off, for example with the aid of cyclones, and recycled intothe chamber. This is preferably effected with a very high circulationrate. Preferred circulation rates are 2 to 100 times, particularlypreferably 5 to 50 times the mass hold-up in the granulator per hour.

In order to have enough spray nuclei to take up the suspension dropletsin this circulating mass, it is necessary to maintain an adequate masshold-up in the system, which is accompanied by a high circulating massstream. The design of the solids separation of the waste gas stream isto be adapted to this high throughput.

A measurement of the pressure loss, for example over the first cycle,can be employed as the measurement parameter for the circulating massstream. At a higher solids loading, the pressure drop over the cycloneincreases under otherwise identical operating conditions. If the cycloneis overloaded and breaks down, the pressure difference reaches a maximumvalue which does not rise further. The operating point to be aimed foris somewhat below this level.

In the upwards flow of the drying chamber, the recycled solid isconveyed upwards past the nozzle. Solid particles and spray dropletsimpinge in the nozzle stream. The liquid dries off on the surface of theparticles, and the solid contained therein remains. As a result, theparticles grow in the circulation layer. To achieve granules which areas spherical as possible, the spray drops must be considerably smallerthan the circulated granules.

The circulating mass must be kept constant, so that after a sufficientmass hold-up has been built up in the granulator, some of the masstherein must be discharged continuously. By decreasing the gas flow ofthe integrated sifter, only the coarse particles are discharged and thefine material remains in the granulator for further building up ofgranules. The sifter is regulated such that the mass circulating in thesystem remains constant.

The particle size to be achieved in the discharge depends on the nucleusbalance in the granulator. This is essentially determined by theequilibrium of nucleus formation by abrasion or non-impinging spraydrops and the build up of granules. The particle size can be increasedin a controlled manner on the one hand by the choice of dryingparameters or on the other hand by addition of binders.

Other drying parameters can thus be established by increasing the amountof feed. As a result, the waste air temperature drops and more spraydroplets are produced, which dry more slowly. The probability ofimpingement on the granule nuclei therefore increases, and in additionthe granule surface remains moist for longer. On average larger nucleiare formed.

The addition of binders increases the firmness of the granules, as aresult of which the abrasion is decreased. Fewer nuclei are thus formed.The average particle size of the granules increases in turn.

The process according to the invention can be supplemented by a productdrying integrated into the process.

The object of the invention is to develop a process for the preparationof approximately spherical, massive particles having a narrow particlesize distribution in the particle size range from 100 μm to 2,000 μm andgood pouring properties (low abrasion, low dust content, good flowproperties) from a solids suspension or a solution.

Preferably, the process is operated for the preparation of feedstuffsadditives such that the average particle size of the animal feedstuffsadditive is established at values of between >0.1 and 2.0 mm. Thediameter of 95% of the particles is preferably in the range between >0.1and 1.2 mm. It is moreover particularly expedient if the diameter of theparticles is established such that it is in the range between 0.3 and0.8 mm in 95% of the particles. In a still further preferred variant ofthe process according to the invention, it is preferable for it to be inthe range between 0.5 and 1.2 mm in 95% of the particles.

A product having a desired bulk density is obtained with the processaccording to the invention in one step from fermentation broth which ispreferably thickened and can be partly or completely freed from thebiomass or in the original state. The bulk density of the animalfeedstuffs additive here is preferably established at >600 kg/m³ to 700kg/m³. In a still further expedient modification of the process, theinvention can be carried out by a procedure in which the bulk density ofthe animal feedstuffs additive is established at >650 kg/m³ to 800 kg/m³in a single step.

In addition, animal feedstuffs additives with an outstanding abrasionresistance of the granules can be obtained by the process according tothe invention. It is thus easily possible, with a suitable processprocedure, to establish the abrasion resistance of the animal feedstuffsadditive at abrasion values in the region of <1.0 wt. %. The process ofthe invention is particularly preferably carried out such that theabrasion resistance of the animal feedstuffs additive is established atan abrasion of between 0 and 0.3 wt. %.

The dry additives accessible according to the invention conventionallycomprise up to 20% of fermentation biomass.

Relatively high amino acid contents of up to max. 90% in the dry masscan be achieved e.g. in the preparation of L-threonine with Escherichiacoli.

In the preparation of L-lysine, L-arginine or L-tryptophan withCorynebacterium glutamicum or Escherichia coli K12 derivatives, theamino acid content is as a rule somewhat lower, and in particular in thecase of tryptophan, by fermentation maximum contents of 70 wt. % arecurrently typical.

Preferably, only one component, in particular an amino acid, ispredominantly present as the active compound in the additive obtainableaccording to the invention. Such an additive can then be metereduniversally into any feed or into premixes according to is activecompound content. In the case of defined feed mixtures, however, it mayalso be expedient for several components, in particular amino acids, tobe present in the additive in a particular ratio to one another, so thatthe desired enrichment is achieved with only one additive. The ratio ofthese active compounds can be obtained, for example, by mixing severalfermentation broths or additives and also by metering in the pure activecompounds of L-amino acids or vitamins. In addition to an individualactive compound or several active compounds, which are contained in atargeted manner or are defined, in the additive, as few as possiblefurther active compounds which are undefined or not suitable forsupplementing should be present in the additive.

To increase the amino acid content in the dry mass or to standardize thedry mass to a particular content of amino acid or to lower the proteincontent of the dry mass, the biomass and optionally other substances canbe removed, preferably after the end of the fermentation, by mechanicalseparation techniques, the predominant contents of the remainingcomponents of the fermentation broth being left.

If no biomass is to be separated off, the fermentation is advantageouslyto be carried out such that as little biomass as possible is produced,in which case the nutrients added should have been consumed as far aspossible at the end. Such a fermentation is described e.g. in DE-A 41 30867, example 3. The fermentation is advantageously carried out such thatover at least 30%, preferably over at least 70% of the duration of thefermentation the concentration of utilizable sugars in the fermentationbroth is not more than 0.3 wt. %.

The granulated feedstuffs additives comprise L-amino acids or vitaminsin an amount of 40 to ˜100 wt. %, preferably 40 to 85 wt. %.

Mutants of the species Corynebacterium or Brevibacterium which arepreferably suitable for lysine are used as microorganisms which produceamino acid.

Hydrolysates of manioc starch (cassava), high fructose corn syrup(HFCS), starch hydrolysates (glucose) or sucrose are preferably employedas the source of carbon. A small content can also originate from sugarbeet or sugar cane molasses. This content should not exceed 5 wt. % ofthe total source of carbon (=10 wt. % of molasses in the total source ofcarbon).

For threonine, tryptophan or pantothenic acid, suitable mutants of thespecies Escherichia coli or Corynebacterium or Corynebacteria arepreferably employed.

In addition to ammonia or ammonium sulfate, hydrolysates ofprotein-containing substances, such as maize gluten, soya flour or thebiomass from a previous batch or, for example, corn steep liquor or fishpeptone, serve as the source of nitrogen.

The fermentation temperature is expediently between 30 and 40° C. andthe pH of the fermentation medium is between 6.0 and 8.0. The durationof the fermentation is in general 100 h and more.

After the end of the fermentation, in general the microorganisms arekilled by means of heat or also by other methods, e.g. by addition of amineral acid, such as sulfuric acid.

The biomass is then optionally completely or partly separated off byknown processes, such as separation, decanting, a combination ofseparating and decanting, ultrafiltration or microfiltration.

The fermentation broth is then thickened by known processes, e.g. in athin film or falling film evaporator, to give a pre-concentrate having asolids content of 30 to 60 wt. %. This pre-concentrate, like thefermentation broth, can then be subjected directly to the processaccording to the invention.

If standardization of the animal feedstuffs additive according to theinvention in respect of the content of L-amino acid is desired, this canbe carried out, for example, by appropriate choice of the amount ofbiomass which remains and/or suitable blending of pre-concentratesand/or fermentation broths. Biomass-free or -reduced broths can also bemixed accordingly with original broths for standardization. Anotherpossibility is the addition of small amounts of additional substanceswhich are acceptable under feedstuffs legislation, such as wheat bran,maize spindle flour or perlites, or also addition of pure L-amino acidsor vitamins.

The animal feedstuffs additives obtainable by the process of theinvention are used for supplementing or preparation of an animalfeedstuff or a premix for animal feedstuffs.

They optionally comprise biomass in an amount of >0 to 20 wt. % (drymass).

Examples

-   1) Purified solutions of L-threonine are sprayed in a circulating    fluidized bed. The purity of the L-threonine was above 98.5% (d₁₀:    10% of the particles have the stated max. particle size).

Temp. of Particle Particle Particle Description feed to Volume size sizesize Bulk Inflow Conc. of feed to the nozzle flow Temperature d10 d50d90 density Circulation speed THR the nozzle ° C. Nm³/h ° C. μm μm μmg/l rate/h m/sec 20% solution 98 650 250 90 268 475 595 30-50 1.8 30%superheated 120 450 350 138 275 620 694 10-30 1.2 solution 40%suspension 120 450 350 127 329 1000 576 10-30 1.2 50% suspension 120 450350 83 204 496 644 10-30 1.2

-   2) Threonine fermentation broths freed from biomass are sprayed in a    circulating fluidized bed. The purity of the L-threonine was 80%.

Temp. of Particle Particle Particle Description feed to the Volume sizesize size Bulk Inflow Conc. of feed to nozzle flow Temperature d10 d50d90 density Circulation speed THR the nozzle ° C. Nm³/h ° C. μm μm μmg/l rate/h m/sec 22.7% solution 95 650 210 120 395 730 650 20-40 1.8

-   3) Calcium pantothenate fermentation broths freed from biomass are    sprayed in a circulating fluidized bed.

The purity of the calcium pantothenate was 55%.

Temp. of Particle Particle Particle Conc. Description feed to Volumesize size size Bulk Inflow cal. of feed to the nozzle flow Temperatured10 d50 d90 density Circulation speed pan. the nozzle ° C. Nm³/h ° C. μmμm μm g/l rate/h m/sec 27.5% solution 95 650 120 170 350 530 650 30-501.8

1-20. (canceled)
 21. A granulated animal feedstuffs additive comprisingL-threonine in an amount of from about 40 to about 100% weight.
 22. Agranulated animal feedstuffs additive, according to claim 21, comprisingL-threonine in an amount of from about 80 to about 100 wt %.
 23. Agranulated animal feedstuffs additive, according to claim 21, whereinsaid granules are substantially spherical.
 24. A granulated animalfeedstuffs additive, according to claim 21, wherein said granules havean average particle size of 0.1 to 2.0 mm.
 25. A granulated animalfeedstuffs additive, according to claim 21, wherein 95% of said granuleshave a diameter in the range between 0.1 and 1.2 mm.
 26. A granulatedanimal feedstuffs additive, according to claim 21, wherein 95% of saidgranules have a diameter in the range between 0.3 and 0.8 mm.
 27. Agranulated animal feedstuffs additive, according to claim 21, wherein95% of said granules have a diameter in the range between 0.5 and 1.2mm.
 28. A granulated animal feedstuffs additive, according to claim 21,wherein said L-threonine is produced by fermentation.
 29. A granulatedanimal feedstuffs additive, according to claim 28, wherein saidL-threonine is produced by Escherichia coli fermentation.
 30. Agranulated animal feedstuffs additive, according to claim 28, whereinsaid L-threonine is produced by Corynebacterium fermentation.
 31. Agranulated animal feedstuffs additive, according to claim 28, whereinsaid granules comprise up to 20 wt % of a fermentation biomass.
 32. Agranulated animal feedstuffs additive, according to claim 28, whereinsaid granules comprise up to 10 wt % of a fermentation biomass.
 33. Agranulated animal feedstuffs additive, according to claim 28, whereinsaid granules comprise up to 5 wt % of a fermentation biomass.
 34. Agranulated animal feedstuffs additive, according to claim 21, whereinsaid granules comprise substantially pure L-threonine.
 35. A granulatedanimal feedstuffs additive, according to claim 21, wherein said granulescomprise L-threonine of up to 99.5% purity.
 36. A granulated animalfeedstuffs additive, according to claim 21, wherein said granules have abulk density of from about 600 to about 70 kg/m³.